Ammonia-water absorption refrigeration unit

ABSTRACT

An ammonia water absorption chiller unit for drive temperatures of also less than 100° C. with at least one absorber arranged in a refrigerant cycle, wherein the absorber includes a fully welded packet of plates for an inner medium which is in turn placed in a casing for an outer medium. A method of minimum complexity for leading media in at least one refrigerant cycle of the ammonia water absorption chiller unit using heat exchangers which include a fully welded packet of plates for an inner medium which is in turn arranged in a casing for an outer medium. A use of an absorber which includes a fully welded packet of plates for an inner medium which is in turn arranged in a casing for an outer medium in a refrigerant cycle of the ammonia water absorption chiller unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of pending Internationalpatent application PCT/EP2010/003301 filed on Jun. 1, 2010 whichdesignates the United States and claims priority from German patentapplication 10 20009 023 929.4 filed on Jun. 4, 2009, the content ofwhich is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to ammonia water absorption chiller unitscomprising at least one absorber arranged in a refrigerant cycle. Thepresent invention furthermore relates to a method of minimum complexityfor leading media in at least one cycle of an ammonia water absorptionchiller unit in consideration of the thermodynamic particularities ofbinary diphase mixtures.

BACKGROUND OF THE INVENTION

The use of an absorber in connection with an ammonia water absorptionchiller unit according to the invention and/or a method according to theinvention is furthermore a subject of the present invention.

The principle of absorption refrigeration by means of the substancecombination of ammonia and water has been known for about 200 years andis mainly used for high refrigerating capacities in the range comprisedbetween about 200 kW and about 6,500 kW today for reducing costs.Installations of this kind, such as for example described in DE 20 2007007 999 U1 require a complex process technology and drive temperaturesof clearly more than 100° C. for cooling temperatures beneath 0° C.

Based upon these facts, an ammonia water absorption chiller unit ofminimum complexity shall be provided by using presently availabletechnologies and new calculation methods for the heat and substancetransfer, which chiller unit permits a more economic application of thecooling principle also for refrigerating capacities of less than 100 kW.In the literature relevant to the subject, see for example VDIWärmeatlas (originally published by VDI-Verlag, Düsseldorf. 10^(th)revised and enlarged edition 2006, ISBN: 978-3-540-25504-8), nocalculation methods are known for this. Thus, up to the present the manskilled in the art does not know any concrete dimensioning guide-linesor methods in order to dimension the individual components of ammoniawater absorption chiller units of minimum complexity for an industriallyusable ammonia water absorption refrigerating machine and to select themcorrespondingly, wherein cooling temperatures beneath 0° C. shall be inparticular achievable with drive temperatures of less than 100° C.

SUMMARY OF THE INVENTION

For technically solving the problem, the invention proposes an ammoniawater absorption chiller unit comprising at least one absorber arrangedin a refrigerant cycle, which is characterized in that the absorbercomprises a fully welded packet of plates for an inner medium which isin turn placed in a casing for an outer medium.

Herein, the invention makes in particular use of the knowledge that iffully welded tube plate exchangers are exclusively used for the absorberof an ammonia water absorption chiller unit, cooling temperatures ofbeneath 0° C. can be achieved even with drive temperatures of less than100° C. with a corresponding dimensioning. Ammonia water absorptionchiller units according to the invention are especially suitable forsolar thermal cooling systems and have been unknown hitherto in thestate of the art. Herein, the present invention is stamped by a newsimplified circuit. In another embodiment of the invention, highlyefficient heat transmitting components are proposed, the combinations ofwhich according to the invention go far beyond the solutions which havebeen hitherto known in the state of the art. The present state of theart proceeds on the assumption that due to the high gas flow rate andthe pressure losses related thereto, an efficient substance and heattransfer in an absorber of an ammonia water absorption chiller unit canonly be obtained by using tubular heat exchangers. According to theinvention it has been found that if the numerous parameters of anammonia water absorption chiller unit are carefully calculated, anefficient heat and substance transfer can be just or especially beachieved by means of tube plate exchangers. Herein, it has surprisinglybeen found that if fully welded tube plate exchangers are exclusivelyused for the absorber of an ammonia water absorption chiller unit,cooling temperatures of beneath 0° C. can be obtained even with drivetemperatures of clearly less than 100° C., in particular if a binaryammonia water diphase mixture is used.

Fully welded packets of plates which can be used according to theinvention for the absorber are typically disclosed in for example EP 1559 981 A2 or DE 601 12 767 T2, the disclosures of which are explicitlyreferenced herewith.

For dimensioning ammonia water absorption chiller units according to theinvention with the object of a highly efficient heat and substancetransfer, the plate geometry of fully welded tube plate exchangers usedfor the absorber is advantageously adapted to or for turbulent flowconditions with pressure losses of less than 0.1 MPa in particularconsideration of the thermodynamic parameters of substance mixtures forleading the media. An adaptation to or for turbulent flow conditions isadvantageously realized with flow rates comprised between 0.05 m/s and 1m/s and with pressure losses of less than 0.1 MPa. Under these specialconditions, drive temperatures beneath 100° C. can also be made usablein an economic way according to the invention.

In an advantageous embodiment of the invention, the absorption takesplace in the casing of the absorber of the ammonia water absorptionchiller unit according to the invention and the generated solution whichis high in refrigerant is pre-stored in the same one. Thus, the solutioncollector which is otherwise common in the state of the art can be savedaccording to the invention. The number of building components of anabsorption chiller unit can thus be reduced and furthermore a compactstructure is achieved. In dependence on the respective application andthe required capacity, an ammonia water absorption chiller unitaccording to the invention can be realized in numerous differentvariants and embodiments, according to the respective need.

In another advantageous embodiment of the invention an evaporator isadvantageously arranged in the refrigerant cycle of the ammonia waterabsorption chiller unit, after or behind which evaporator, the absorberfollows in flow direction. Thereby the flow dependent pressure lossesare reduced and the efficiency of an ammonia water absorption chillerunit according to the invention is further improved. The evaporatoradvantageously comprises a fully welded packet of plates for an innermedium, which is in turn arranged in a casing for an outer medium. Inthe packet of plates, a change of phases of the liquid refrigerant intothe gaseous state preferably occurs. Herein, the refrigerant constantlywithdraws the heat from the medium in the casing of the refrigeratingagent cycle which shall be cooled by means of the absorption chillerunit. The currents in the packet of plates and in the casing of theevaporator are preferably guided in reverse currents with respect toeach other. Fully welded packets of plates which can be used accordingto the invention for the evaporator are typically disclosed by forexample EP 1 559 981 A2 or DE 601 12 767 T2.

In another advantageous embodiment of the invention, a desorber(desorption unit) is advantageously arranged in the refrigerant cycle ofthe ammonia water absorption chiller unit, advantageously comprising afully welded packet of plates for an inner medium which is in turnarranged in a casing for an outer medium. In the desorber, preferably inthe packet of plates, a change of phases of the refrigerant bearingsolution from the liquid into the gaseous state occurs. Herein, therefrigerant bearing solution is constantly supplied with heat by amedium in the casing of the heating cycle which drives or shall drivethe absorption chiller unit. The currents in the packet of plates and inthe casing of the desorber are preferably guided in reverse currentswith respect to each other. The desorber is advantageously arrangedafter the absorber in the refrigerant flow direction. Thanks to thesemeasures according to the invention, taken individually or incombination with each other, the efficiency of an ammonia waterabsorption chiller unit will be further improved. Fully welded packetsof plates which can be used according to the invention for the desorberare typically disclosed by for example EP 1 559 981 A2 or DE 601 12 767T2.

In another advantageous embodiment of the invention, a condenser isadvantageously arranged in the refrigerant cycle of the ammonia waterabsorption chiller unit, advantageously comprising a fully welded packetof plates for an inner medium which is in turn arranged in a casing foran outer medium. In the condenser, preferably in the casing, a change ofphases of a refrigerant bearing vapor from the gaseous into the liquidstate occurs, wherein the generated refrigerant bearing condensate willbe pre-stored in the same one. Thereby, the refrigerant collector whichis otherwise common in absorption chiller units according to the stateof the art can be saved. The number of building components of an ammoniawater absorption chiller unit is thus reduced and a compact structure isenabled. Herein, the refrigerant bearing vapor constantly conveys heatto a medium in the packet of plates of the recooling cycle which servesas heat sink to the ammonia water absorption chiller unit according tothe invention. The currents in the packet of plates and in the casing ofthe condenser are preferably guided in reverse currents with respect toeach other. The condenser is advantageously arranged before theevaporator of an ammonia water absorption chiller unit according to theinvention in the refrigerant flow direction. Thanks to these measuresaccording to the invention, taken individually or in combination witheach other, in particular the efficiency of an ammonia water absorptionchiller unit will be further improved. Fully welded packets of plateswhich can be used according to the invention for the condenser aretypically disclosed by for example EP 1 559 981 A2 or DE 601 12 767 T2.

In another advantageous embodiment of the invention, a solution heatexchanger is advantageously arranged in the refrigerant cycle of theammonia water absorption chiller unit, advantageously comprising a fullywelded packet of plates for an inner medium which is in turn arranged ina casing for an outer medium. In the solution heat exchanger, arefrigerant bearing solution which shall be supplied to the desorberwill be internally pre-heated. The currents in the packet of plates andin the casing of the solution heat exchanger are preferably guided inreverse currents with respect to each other. Thereby, the external heatsupply will be reduced in the desorber and the efficiency of an ammoniawater absorption chiller unit according to the invention will be furtherimproved. The solution heat exchanger is preferably arranged between theabsorber and the desorber in the refrigerant flow direction. Thanks tothese measures according to the invention, taken individually or incombination with each other, in particular the efficiency of an ammoniawater absorption chiller unit according to the invention will be furtherimproved. Fully welded packets of plates which can be used according tothe invention for the solution heat exchanger are typically disclosed byfor example EP 1 559 981 A2 or DE 601 12 767 T2.

In another advantageous embodiment of the invention, a dephlegmator isadvantageously arranged in the refrigerant cycle of the ammonia waterabsorption chiller unit at drive temperatures of more than 100° C.,advantageously comprising a fully welded packet of plates for an innermedium which is in turn arranged in a casing for an outer medium. In thedephlegmator, preferably in the packet of plates a refrigerant bearingvapor which shall be supplied to the condenser conveys heat to a mediumin the casing, wherein a part of the refrigerant bearing vapor alreadycondenses. Thereby it is achieved that only small quantities of solventvapor reach the condenser. The dephlegmator is preferably arrangedbefore the condenser in the refrigerant flow direction. Thanks to thesemeasures according to the invention, taken individually or incombination with each other, in particular the efficiency of an ammoniawater absorption chiller unit according to the invention will be furtherimproved. Fully welded packets of plates which can be used according tothe invention for the dephlegmator are typically disclosed by forexample EP 1 559 981 A2 or DE 601 12 767 T2.

According to an especially advantageous embodiment of the invention itis possible to omit building components which have been hitherto assumedas necessary or required in the state of the art. It has been found thatat drive temperatures of less than 100° C. the portion of vaporoussolvent in the refrigerant bearing vapor is usually less than 5%, suchthat according to the need in particular a dephlegmator can be savedaccording to the invention.

In another advantageous embodiment of the invention, a refrigerantsupercooling unit is arranged in the refrigerant cycle of the ammoniawater absorption chiller unit, advantageously comprising a fully weldedpacket of plates for an inner medium which is in turn arranged in acasing for an outer medium. In the refrigerant supercooling unit, thetemperature of the condensed refrigerant which shall be supplied to theevaporator is reduced beneath the boiling point. Thereby it is achievedaccording to the invention that, on the one hand, no prematureevaporation occurs with pressure losses and, on the other hand, theamount of the evaporation enthalpy is increased which further improvesthe efficiency of an ammonia water absorption chiller unit according tothe invention. The currents in the packet of plates and in the casing ofthe refrigerant supercooling unit are preferably guided in reversecurrents with respect to each other. The refrigerant supercooling unitis preferably arranged between the evaporator and the condenser, on theone hand, and between the evaporator and the absorber, on the otherhand, in the refrigerant flow direction. Fully welded packets of plateswhich can be used according to the invention for the refrigerantsupercooling unit are typically disclosed by for example EP 1 559 981 A2or DE 601 12 767 T2.

According to an especially advantageous embodiment of the invention itis possible to omit building components which have been hitherto assumedas necessary or required in the state of the art. It has been found thatwith a cooling capacity of the evaporator of less than 100 kW, therefrigerant supercooling unit can also be saved, in particular sincewith a cooling capacity of the evaporator of less than 100 kW thecontribution of a refrigerant supercooling unit to increasing theefficiency of an ammonia water absorption chiller unit according to theinvention does not justify the technical expenditure and the costsrelated thereto for an efficient use.

The refrigerant contained in the refrigeration cycle is preferablyammonia or comprises ammonia. The solvent contained in the refrigerationcycle is preferably water or comprises water.

In another advantageous embodiment of the invention, the feeding pipesand/or draining pipes to the condenser and/or the absorber in therefrigerant flow direction are provided with a pressure compensationpipe. Thereby, pressure losses are reduced and a more uniform heattransfer is enabled. Thanks to this measure which is unusual in thestate of the art the efficiency of the absorption of refrigerant insorbent and thus the efficiency of an ammonia water absorption chillerunit according to the invention will be further improved.

The invention furthermore relates to ammonia water absorption chillerunits comprising an absorption refrigeration method of minimumcomplexity for leading media in at least one refrigerant cycle usingheat exchangers which comprise a fully welded packet of plates for aninner medium which is in turn arranged in a casing for an outer medium.Fully welded packets of plates which can be used according to theinvention are typically disclosed by for example EP 1 559 981 A2 or DE601 12 767 T2.

According to the invention, it is proposed that in particularconsideration of the thermodynamic of substance mixtures for leading themedia the plate geometry is adapted to turbulent flow conditions withpressure losses of less than 0.1 MPa for a particularly efficient heatand substance transfer. An adaptation to or for turbulent flowconditions is advantageously realized with flow rates comprised between0.05 m/s and 1 m/s and with pressure losses of less than 0.1 MPa.According to the invention, it becomes simultaneously possible therebyto obtain a compact construction of ammonia water absorption chillerunits according to the invention. In dependence on the respectiveapplication and the required capacity, the embodiment according to theinvention can be realized in numerous different variants, according tothe respective need. Herein, the modular graduation and adaptation offully welded tube plate exchangers permits to use the method withcooling capacities comprised between the kilowatt range and the megawattrange and the method can thus considerably contribute to an economic useof energy advantageously.

Logically, the invention furthermore relates to an absorber which isconfigured as fully welded packet of plates for an inner medium which isin turn arranged in a casing for an outer medium, in a refrigerant cycleof an ammonia water absorption chiller unit according to the inventionin particular having one or more of the above mentioned characteristics.

The embodiments according to the invention and the knowledge gained bythem permit an optimization of the individual tube plate exchangers,lead to a high efficiency and allow a compact construction of ammoniawater absorption chiller units which has been hitherto unknown andinaccessible in the state of the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Other details, characteristics and advantages of the invention will beexplained in detail in the following by means of the exemplaryembodiment of the invention which is represented in the FIGURE of thedrawing. Herein:

FIG. 1 is a block diagram which shows an exemplary embodiment of anammonia water absorption chiller unit according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an ammonia water absorption chiller unit 1 comprising anabsorber 10, an evaporator 20, a condenser 30, a desorber 40, a solutionheat exchanger 50, a dephlegmator 60 and a refrigerant supercooling unit70 which are arranged in a refrigerant cycle 2. Furthermore, pressurecompensation pipes 80, 90 realize a connection in the refrigerant flowdirection 3 between the feeding and draining pipe of the absorber 10 orthe condenser 30 in order to reduce pressure losses and to permit a moreuniform heat transfer.

The refrigerant contained in the refrigerant cycle 2 flows into therefrigerant flow direction 3 which is symbolically represented by meansof an arrow and is supplied by means of a pump 100 into the desorber 40.The principal functioning of an absorption chiller unit is presentlytaken for granted (cf. in particular Handbuch der Kältetechnik, vol. 7,sorption refrigerating machines, Wilhelm Niebergall, 1959). The driveenergy is introduced and discharged via a heating medium through theconnections 41 and 42 into or from the desorber 40. The cooling effectis transferred by means of a refrigerant medium in the evaporator 20through the connections 21 and 22. The recooling of the ammonia waterabsorption chiller unit 1 is realized by a heat transfer medium in theabsorber 10 through the connections 11 and 12 as well as in thecondenser through the connections 31 and 32. The design of the heatexchanger which comprises a fully welded packet of plates for an innermedium which is turn arranged in a casing for an outer mediumprincipally follows the disclosures of EP 1 559 981 A2 or DE 601 12 767T2, the disclosures of which are explicitly referenced herewith. Theplate geometry of a fully welded packet of plates according to theinvention is advantageously adapted to turbulent flow conditions withflow rates comprised between 0.05 m/s and 1 m/s and with pressure lossesof less than 0.1 M Pa in particular consideration of the thermodynamicof substance mixtures for leading the media for a particularly efficientheat and substance transfer.

The improvement of the invention presently refers to a reduction ofcomponents of an absorption chiller unit which has been hithertoregarded as impossible or unrealizable in the state of the art and whichcomponents have been hitherto regarded as required and necessary. Theresults and calculations of the present invention show that thedephlegmator 60 can be saved with drive temperatures of less than 100°C. The same is true for the refrigerant supercooling unit 70 with acooling capacity of the evaporator of less than 100 kW. Under thesecircumstances, ammonia water absorption chiller units 1 of minimumcomplexity are obtained which allow an economic application of thecooling principle also for cooling capacities of less than 100 kW, atdrive temperatures of less than 100° C. and cooling temperatures of lessthan 0° C.

The exemplary embodiments of the invention represented in the FIGURE ofthe drawing and described in connection with this one only serve forexplaining the invention and are not limiting to this one.

LIST OF REFERENCE NUMERALS

-   -   1 absorption chiller unit    -   2 refrigerant cycle    -   3 refrigerant flow direction    -   10 absorber    -   11 connection    -   12 connection    -   20 evaporator    -   21 connection    -   22 connection    -   30 condenser    -   31 connection    -   32 connection    -   40 desorber    -   41 connection    -   42 connection    -   50 solution heat exchanger    -   60 dephlegmator    -   70 refrigerant supercooling unit    -   80 pressure compensation pipe    -   90 pressure compensation pipe    -   100 pump

1. An ammonia water absorption chiller unit comprising at least oneabsorber arranged in a refrigerant cycle, characterized in that theabsorber comprises a fully welded packet of plates for an inner mediumwhich is in turn placed in a casing for an outer medium.
 2. The ammoniawater absorption chiller unit according to claim 1, characterized by anevaporator arranged in the refrigerant cycle, comprising a fully weldedpacket of plates for an inner medium which is in turn placed in a casingfor an outer medium.
 3. The ammonia water absorption chiller unitaccording to claim 2, characterized in that the absorber is arrangedafter the evaporator in the refrigerant flow direction.
 4. The ammoniawater absorption chiller unit according to claim 1, characterized by adesorber arranged in the refrigerant cycle, comprising a fully weldedpacket of plates for an inner medium which is in turn placed in a casingfor an outer medium.
 5. The ammonia water absorption chiller unitaccording to claim 4, characterized in that the desorber is arrangedafter the absorber in the refrigerant flow direction.
 6. The ammoniawater absorption chiller unit according to claim 1, characterized by acondenser arranged in the refrigerant cycle, comprising a fully weldedpacket of plates for an inner medium which is in turn placed in a casingfor an outer medium.
 7. The ammonia water absorption chiller unitaccording to claim 1, characterized in that the condenser is arrangedbefore the evaporator in the refrigerant flow direction.
 8. The ammoniawater absorption chiller unit according to claim 1, characterized by asolution heat exchanger arranged in the refrigerant cycle, comprising afully welded packet of plates for an inner medium which is in turnplaced in a casing for an outer medium.
 9. The ammonia water absorptionchiller unit according to claim 8, characterized in that the solutionheat exchanger is arranged between the absorber and the desorber in therefrigerant flow direction.
 10. The ammonia water absorption chillerunit according to claim 1, characterized in that at drive temperaturesof more than 100° C. a dephlegmator which is arranged in the refrigerantcycle and comprises a fully welded packet of plates for an inner mediumwhich is in turn placed in a casing for an outer medium is present. 11.The ammonia water absorption chiller unit according to claim 10,characterized in that the dephlegmator is arranged before the condenserin the refrigerant flow direction.
 12. The ammonia water absorptionchiller unit according to claim 10, characterized in that thedephlegmator is cancelled at drive temperatures of less than 100° C. 13.The ammonia water absorption chiller unit according to claim 1,characterized by a refrigerant supercooling unit arranged in therefrigerant cycle, comprising a fully welded packet of plates for aninner medium which is in turn placed in a casing for an outer medium.14. The ammonia water absorption chiller unit according to claim 13,characterized in that the refrigerant supercooling unit is cancelledwith a cooling capacity of the evaporator of less than 100 kW.
 15. Theammonia water absorption chiller unit according to claim 13,characterized in that the refrigerant supercooling unit is arrangedbetween the evaporator and the condenser, on the one hand, and betweenthe evaporator and the absorber, on the other hand, in the refrigerantflow direction.
 16. The ammonia water absorption chiller unit accordingto claim 1, characterized in that the refrigerant cycle comprises atleast one refrigerant, preferably ammonia.
 17. The ammonia waterabsorption chiller unit according to claim 1, characterized in that therefrigerant cycle comprises at least one solvent, preferably water. 18.The ammonia water absorption chiller unit according to claim 1,characterized in that the feeding pipes and/or draining pipes to thecondenser and the absorber in the refrigerant flow direction containpressure compensation pipes.
 19. A method of minimum complexity forleading media in at least one refrigerant cycle of an ammonia waterabsorption chiller unit, preferably an ammonia water absorption chillerunit according to claim 1, using heat exchangers which comprise a fullywelded packet of plates for an inner medium which is in turn arranged ina casing for an outer medium.
 20. The method according to claim 19,characterized in that for leading the media the plate geometry of theheat exchangers is adapted to turbulent flow conditions for aparticularly efficient heat and substance transfer.
 21. The methodaccording to claim 20, characterized by an adaptation of the plategeometry of the heat exchangers to or for turbulent flow conditions withflow rates comprised between 0.05 m/s and 1 m/s as well as with pressurelosses of less than 0.1 MPa.
 22. A use of an absorber which comprises afully welded packet of plates for an inner medium which is in turnarranged in a casing for an outer medium, in a refrigerant cycle of anammonia water absorption chiller unit, preferably an ammonia waterabsorption chiller unit preferably using a method according to claim 19.